Early High-contrast Imaging Results with Keck/NIRC2-PWFS: The SR 21 Disk

Taichi Uyama, Bin Ren, Dimitri Mawet, Garreth Ruane, Charlotte Z. Bond, Jun Hashimoto, Michael C. Liu, Takayuki Muto, Jean Baptiste Ruffio, Nicole Wallack, Christoph Baranec, Brendan P. Bowler, Elodie Choquet, Mark Chun, Jacques Robert Delorme, Kevin Fogarty, Olivier Guyon, Rebecca Jensen-Clem, Tiffany Meshkat, Henry NgoJason J. Wang, Ji Wang, Peter Wizinowich, Marie Ygouf, Benjamin Zuckerman

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


High-contrast imaging of exoplanets and protoplanetary disks depends on wave front sensing and correction made by adaptive optics instruments. Classically, wave front sensing has been conducted at optical wavelengths, which made high-contrast imaging of red targets such as M-type stars or extincted T Tauri stars challenging. Keck/NIRC2 has combined near-infrared (NIR) detector technology with the pyramid wave front sensor (PWFS). With this new module we observed SR 21, a young star that is brighter at NIR wavelengths than at optical wavelengths. Compared with the archival data of SR 21 taken with the optical wave front sensing we achieved ∼20% better Strehl ratio in similar natural seeing conditions. Further post-processing utilizing angular differential imaging and reference-star differential imaging confirmed the spiral feature reported by the Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch instrument polarimetric observation, which is the first detection of the SR 21 spiral in total intensity at L′ band. We also compared the contrast limit of our result (10-4 at 0.″4 and 2 10-5 at 1.″0) with the archival data that were taken with optical wave front sensing and confirmed the improvement, particularly at ≤0.″5. Our observation demonstrates that the NIR PWFS improves AO performance and will provide more opportunities for red targets in the future.

Original languageEnglish (US)
Article number283
JournalAstronomical Journal
Issue number6
StatePublished - Dec 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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